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  Optical reading apparatusUSPTO Application #: 20060239136Title: Optical reading apparatus Abstract: In an optical reading apparatus, a light source, a high frequency modulator IC and a first resistor are integrated in an optical pickup unit, wherein the light source emits a light beam onto the optical storage medium in order to read information from the optical storage medium, the high frequency modulator generates a high frequency modulating signal for adjusting the intensity of the light beam, and the first resistor has a first end coupled to ground and a second end couple to a first pin of the high frequency modulator IC. A voltage control module disposed outside the optical pickup unit and coupled to the first resistor in parallel is used for adjusting an output current of the first pin in response to a voltage change thereof, thereby adjusting the amplitude of the high frequency modulating signal. (end of abstract)
Agent: Madson & Austin Gateway Tower West - Salt Lake City, UT, US Inventors: Jen-Yu Hsu, Hsiang-Yi Fu, Fu-Hsiang Chen, Ming-Hsiao Tsai USPTO Applicaton #: 20060239136 - Class: 369044120 (USPTO) Related Patent Categories: Dynamic Information Storage Or Retrieval, With Servo Positioning Of Transducer Assembly Over Track Combined With Information Signal Processing, Optical Servo System, Solid State Optical Element With Plural Dissimilar Optical Components (e.g., Using I.c. Block, Etc.) The Patent Description & Claims data below is from USPTO Patent Application 20060239136. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates to an optical reading apparatus such as an optical disc drive, and more particularly to an optical reading apparatus adopting high frequency modulation. BACKGROUND OF THE INVENTION [0002] FIG. 1 shows an optical pickup unit (OPU) of a typical optical disc drive. A light beam emitted from a laser diode 10 is focused on the surface of an optical disk 1 through an optical system 11 including a set of lens and mirrors. The reflected light beam from the optical disk 1 through the optical system 11 is converted to an electronic signal by a photodiode 12. The incident and reflective light paths in the OPU of FIG. 1 are separately shown in the FIG. 2(a) and 2(b). As shown in FIG. 2(a), the incident light beam is emitted from the laser diode 10 and transmitted through the optical system 11 to reach the surface of the optical disk 1. Afterwards, as shown in FIG. 2(b), the light beam carrying information of the optical disc 1 is reflected from the surface of the optical disk 1 and transmitted through the optical system 11 to the photodiode 12 to be analyzed. As clearly shown in FIG. 1, there is an overlapping portion between the incident and reflective optical paths so as to likely cause undesired interference between the incident light beam and the reflected light beam. Therefore, the resulting electronic signal generated by the photodiode 12 would be adversely affected by the interference and the data reading/writing accuracy would thus be deteriorated. [0003] For this reason, high frequency modulation (HFM) technology is developed for minimizing the interference effect of the incident light beam on the reflected light beam. According to the HFM technology, a high frequency modulating signal is superimposed to the driving current of the laser diode 10 to differentiate the light beams. For implementing the HFM technology, a high frequency modulator integrated circuit 3 as shown in FIG. 3(a) is used. Since the HFM technology has been widely used, there is no need to go into details herein. [0004] However, the HFM technology is likely to cause some problems. For example, referring to FIG. 3(a), the amplitudes of the high-frequency modulating signals are adjusted according to the resistance values of the external resistors Ramp1 and Ramp2 connected separately to pin numbers 15 and 16 of the IC 3. Also, the frequencies of the high-frequency modulating signals are adjusted according to the resistance values of the external resistors Rfreq1 and Rfreq2 connected separately to pin numbers 2 and 3 of the IC 3. Therefore, driving currents superimposing high-frequency modulating signals with adjustable amplitude and frequency are outputted from pin numbers 18 and 13 to the laser diodes LD1 and LD2. In general, the amplitude of the high-frequency modulating signal decreases with the increase of the resistance coupled thereto. For enhancing data-reading accuracy, a high-frequency modulating signal with high amplitude is desirable. Unfortunately, the higher the amplitude of high frequency modulation signal is, the more significant the electromagnetic interference (EMI) of the optical disc drive is. Accordingly, the high-frequency modulating signal with too high amplitude would cause the optical disc drive fails in the EMI test. Therefore, the designer has to select and mount suitable external resistors in order to adjust the amplitudes of the high frequency modulation signals within an optimal range, which may require replacement of external resistors again and again. [0005] As the high-frequency modulator IC 3 and the resistors are all disposed inside the optical pickup unit of the optical disc drive. The process of replacing resistors would be too complicated to be cost- and laboring-efficient. [0006] FIG. 3(b) shows the frequency spectrum of the high frequency modulation signal outputted by the IC 3 of FIG. 3(a), which is centralized around a certain frequency, e.g. about 300 MHz for a CD laser and about 350 MHz for a DVD laser. In addition to high amplitude, the highly centralized feature of the high frequency modulation signal also intensifies the EMI effect. SUMMARY OF THE INVENTION [0007] Therefore, an object of the present invention is to design an optical reading apparatus for conveniently adjusting the amplitude of the high frequency modulating signal so as to reduce the EMI effect and thus improve the data-reading quality. [0008] Another object of the present invention is to design an optical reading apparatus for well distributing the frequency of the high frequency modulating signal so as to reduce the EMI effect and thus improve the data-reading quality. [0009] The present invention provides an optical reading apparatus for reading an optical storage medium. The optical reading apparatus comprises an optical pickup unit integrated therein a light source, a high frequency modulator IC and a first resistor, wherein the light source emits a light beam onto the optical storage medium in order to read information from the optical storage medium, the high frequency modulator generates a high frequency modulating signal for adjusting the intensity of the light beam, and the first resistor has a first end coupled to ground and a second end couple to a first pin of the high frequency modulator IC. The optical reading apparatus further comprises a voltage control device coupled to the first resistor in parallel for adjusting an output current of the first pin in response to a voltage change thereof, thereby adjusting the amplitude of the high frequency modulating signal. The voltage control device can be a voltage control module disposed outside the optical pickup unit. [0010] In an embodiment, the voltage control device comprises a register for storing a digital data that is mapped to a voltage value; a digital-to-analog converter coupled to the register for converting the digital data to the voltage value; an amplifying circuit coupled to the digital-to-analog converter for receiving the voltage value and generating and outputting a corresponding current; and an output resistor coupled between the amplifying circuit and the second end of the first resistor in series, and flowing therethough the current outputted by the amplifying circuit. The summation of the output current of the first pin and the current flowing through the output resistor is equal to the current flowing through the first resistor, which is a constant. [0011] In another embodiment, the voltage control module comprises a variable voltage source for outputting a variable voltage value; and an output resistor coupled between the variable voltage source and the second end of the first resistor in series, wherein the output current of the first pin changes with the current flowing through the output resistor. [0012] In an embodiment, the optical reading apparatus further comprises a second resistor integrated in the optical pickup unit and coupled to a second pin of the high frequency modulator IC; and an AC voltage source grounded by one end thereof and coupled to the second pin of the high frequency modulator IC in parallel to the second resistor by another end thereof for dispersing the frequency of the high frequency modulating signal. [0013] The present invention also provides an optical reading apparatus for reading an optical storage medium, which comprises an optical pickup unit integrated therein a light source, a high frequency modulator IC and a first resistor, wherein the light source emits a light beam onto the optical storage medium in order to read information from the optical storage medium, the high frequency modulator generates a high frequency modulating signal for adjusting the intensity of the light beam, and the first resistor has a first end grounded and a second end couple to a first pin of the high frequency modulator IC; and a voltage control module disposed outside the optical pickup unit and coupled to the first resistor in parallel for adjusting an output current of the first pin in response to a voltage change thereof, thereby adjusting the amplitude of the high frequency modulating signal. The optical reading apparatus can further comprise a second resistor integrated in the optical pickup unit and coupled to a second pin of the high frequency modulator IC; and an AC voltage source grounded by one end thereof and coupled to the second pin of the high frequency modulator IC in parallel to the second resistor by another end thereof for dispersing the frequency of the high frequency modulating signal. The voltage change of the voltage control module can be conducted from the external. BRIEF DESCRIPTION OF THE DRAWINGS [0014] The above contents of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: [0015] FIG. 1 is a schematic block diagram showing an optical pickup unit (OPU) of an optical disc drive; [0016] FIG. 2(a) is a schematic block diagram showing the optical path of the incident light beam in the optical pickup unit; [0017] FIG. 2(b) is a schematic block diagram showing the optical path of the reflected light beam in the optical pickup unit; [0018] FIG. 3(a) is a circuit layout and pin list of a high-frequency modulator IC and circuitry coupled thereto according to prior art; [0019] FIG. 3(b) is a schematic frequency spectrum of a high frequency modulation signal outputted by the high-frequency modulator IC of FIG. 3(a); [0020] FIG. 4 is a circuit layout of a high-frequency modulator IC disposed in an optical pickup unit and associated circuitry according to an embodiment of the present invention; Continue reading... Full patent description for Optical reading apparatus Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Optical reading apparatus patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Optical reading apparatus or other areas of interest. ### Previous Patent Application: Optical disk changer with side switching capabilities Next Patent Application: Optical pickup actuator and optical recording and/or reproducing apparatus Industry Class: Dynamic information storage or retrieval ### FreshPatents.com Support Thank you for viewing the Optical reading apparatus patent info. 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